The elevator system is installed in a shaft. It essentially consists of an elevator car which is connected by way of suspension means with a counterweight. The car is moved along a substantially vertical guide track by means of a drive which selectably acts on the suspension means, directly on the car or directly on the counterweight. In a normal operating mode the elevator car is accelerated by the drive in correspondence with a normal travel plot, kept in constant motion and again decelerated. A holding brake controlled together with the drive fixes the elevator car at standstill. An elevator regulating algorithm by means of which a travel plot can be regulated in the normal operating mode of an elevator car to be as comfortable as possible is shown in U.S. Pat. No. 4,130,184. In this connection, in particular, travel plots are demonstrated which take into consideration the fact that a maximum travel speed cannot be achieved with short travel distances or floor spacings. According to U.S. Pat. No. 4,130,184, for short floor spacings there is direct transition from a regulated acceleration phase to a regulated deceleration phase.
If the elevator car departs from the normal travel plot usual in normal operation this is detected by a safety monitoring system. The moved elevator car is then, in a special operating mode, decelerated to standstill by brake equipment by means of a braking force, which is produced by the brake equipment together with a brake track, and subsequently held at standstill. A special operating mode arises when an intended travel sequence has to be interrupted due to a fault and accordingly it is not possible to travel to a planned destination stopping point. This includes, for example, departure of an effective travel movement from the normal travel plot, an interruption of drive energy, a failure of operating-mode brake systems or also a failure of the suspension means.
EP 1792864 shows brake equipment of that kind in the form of a safety brake. In this regard the safety brake is actuated, which rapidly and safely stops the elevator car, if fault behavior is detected. The braking force is produced in these items of braking equipment in that a brake lining is pressed by a force against the brake track. This pressing force is termed normal force and the braking force results from this normal force and a coefficient of friction specific to a brake pairing. The brake pair is defined by the brake lining and the brake track.
Another elevator system of that kind or brake equipment is known from EP 0648703. In this connection the elevator car is, in a special operating mode, decelerated and held at standstill by means of regulable brake equipment independent of the drive.
A disagreeable aspect of these elevator systems is that after response of this brake equipment in the special operating mode the elevator car comes to a stop at random. A long waiting time usually follows until service personnel are on site in order to free any trapped persons. Moreover, there is no solution as to how the state of a stationary car can be recognized in order to securely hold it after standstill has taken place. It would be obvious for this purpose to make use of a signal of a speed sensor from which naturally a standstill state can be recognised.